1. Field of the Invention
This invention generally relates to a dual mode communication control apparatus having both of a direct communication mode and a store and forward communication mode, and, in particular, to a store and forward switching type communication control apparatus connected between a plurality of internal and external lines.
2. Description of the Prior Art
A store and forward switching type communication apparatus capable of once storing image information to be transmitted in a memory and then transmitting the thus stored image information to a destination station has recently attracted attention due to the recent rapid dissemination of facsimile machines. Such a store and forward switching type communication apparatus has two modes of operation, i.e., (1) a direct communication mode, in which one of the internal lines is directly connected to one of the external lines to carry out communication in response to a call received through either an internal or external line and (2) a store and forward communication mode, in which, when a call has been received from one of the internal lines, the image information transmitted through this internal line is once stored in a memory, and then the thus stored image information is transmitted to a destination station at a designated time.
In the direct communication mode, the store and forward switching type communication control apparatus carries out a sequence of operation, including the steps of (1) off-hook from a telephone unit or a facsimile machine connected to one of the internal lines; (2) apprising of the off-hook status to a control unit through an interface of the internal line; (3) securing of resources of the internal line interface by the control unit; (4) designating a connection between the internal line interface and a DT (dial tone) sound source from the control unit to a switching unit; (5) inputting (designation of operation and the telephone number of the destination station) by dialing (dial pulse signal (DP) or push button signal (PB)) from the internal line side; (6) designating a release of connection between the internal line interface and the DT sound source from the control unit to the switching unit; (7) securing of an external line interface; (8) instructing the external interface to place a call to the destination station; (9) designating a connection between the internal interface and the external interface from the control unit to the switching unit; (10) initiation of facsimile communication (or aural communication); (11) off-hook from the internal line side; (12) apprising of the off-hook status to the control unit from the internal interface; and (13) releasing of the resources (disconnecting the switching unit from the internal and external interfaces).
On the other hand, during the store and forward communication mode, the store and forward communication apparatus carries out a sequence of steps, which include: (1) off-hook signal from a telephone unit or facsimile machine connected to an internal line; (2) apprising of the off-hook status to the control unit from the internal line interface; (3) securing of resources of the internal line interface by the control unit; (4) designating a connection between the internal line interface and a DT sound source from the control unit to the switching unit; (5) inputting (designation of operation and the telephone number of the destination station) by dialing (DP or PB) from the internal line side; (6) instructing the switching unit to release a connection between the internal line interface and the DT sound source from the control unit; (7) apprising a store and forward communication operation and the telephone number of the destination station to the control unit from the internal line interface; (8) designating a connection between the internal line interface and a communicating means for facsimile communication from the control unit to the switching unit; (9) instructing a reception operation to the communicating means for facsimile communication from the control unit; (10) designating transmission to a facsimile machine connected to the internal line; (11) initiation of facsimile communication; (12) storing of received image information into storing means from the communicating means for facsimile communication; (13) completion of facsimile communication; (14) off-hook signal from the internal line; (15) apprising of off-hook from the internal line interface to the control unit; and (16) releasing of the resources (disconnection among the internal line interface, the communication means for facsimile communication and the switching unit).
With this structure, since a plurality of communication terminals, such as telephone units and/or facsimile machines, can be managed by a common store and forward switching communication control apparatus, the use rate of a transmission network can be significantly enhanced. However, in such a prior art store and forward switching type communication control apparatus, when transmission is to be carried out from an internal line to an external line, it is only after inputting of operational instructions and the telephone number of a destination station by an operator of a communication terminal connected to the internal line that the status of various resources of the communication control apparatus, such as interfaces, transmission lines, communicating means and storing means, is checked and securing of resources is carried out. Thus, there is a case in which, even if a dial tone is properly generated during off-hook, required resources cannot be secured by a dialing operation because such resources as interfaces and transmission lines are in the busy status, thereby waisting the operation by the operator. In this case, the exactly the same operation must be repeated by the operator and thus there is a lack of easiness or convenience in operation.